Phonographs produce sound through the mechanical vibration of a stylus. In older phonographs, known as gramophones, sound was produced through a strictly mechanical linkage between the stylus, a diaphragm, and a sound horn. In later versions (after about 1930) an electromagnetic stylus would convert translational or vertical movement to an electrical signal that was amplified to drive a loudspeaker. Different types of electromechanical styli include moving magnet, moving iron and moving coil cartridges. Through the 1940's and 50's mechanical styli were almost entirely replaced by electromagnetic ones.